Pusher attachment for lift trucks



June 19, 1962 D. R. HOYT ETAL 3,039,636

PUSHER ATTACHMENT FOR LIFT TRUCKS Filed Dec. 12, 1958 3 Sheets-Sheet 1I. o 6 m 0 LI. N g Q m P8 0 9 R5 W l H v 0 T a;

INVENTORS.

DERYL. R. HOYT DARYL W. STEVENS ATTY.

June 19, 1962 D. R. HOYT ETAL 3,039,636

PUSHER ATTACHMENT FOR LIFT TRUCKS Filed Dec. 12, 1958 s Sheets-Sheet 2FICB. 2

INVENTORS. 'DERYL R. HOYT DARYL W. STEVENS ATTY.

June 19, 1962 D. R. HOYT ETAL 3,039,636

PUSHER ATTACHMENT FOR LIFT TRUCKS Filed Dec. 12, 1958 3 Sheets-Sheet 3INVENTORS. DERYL R. HOYT DARYL W. STEVENS ATTY.

United States The present invention relates generally to attachments forindustrial lift trucks, and specifically to improved pusher means whichmay be employed for selectively discharging a load from such a truck.

Industrial lift trucks are extensively used in the handling of goodssuch as logs. The load supporting carriage of the conventional truck isprovided with forks having horizontal forwardly extending loadsupporting portions upon which the logs are stacked for transportation;the load supporting carriage ordinarily is arranged for verticalmovement on a mast structure which is tiltable forwardly through a smallangle. After the logs have been transported to the place of deposit, thelogs heretofore have usually been rolled off the forks by tilting themast forwardly, or by placing the logs on dunnage and withdrawing theforks. In the case of logs having a flat side, or in unloading logswhere dunnage is not available, or in placing logs on top of othen logs,the forward tilt available may not be adequate to insuredischarge of thelogs, and attempts to withdraw the forks from under a log may pull overthe whole pile or otherwise be dangerous to workmen engaged in unloadingand piling the logs;

US. Patent No. 2,742,167 to R. A. Brudi, dated April 17, 1956, disclosesa remotely operable pusher device for use with industrial lift truckswhich is employed for discharging a load such as logs from the forks ofa lift truck, and constitutes an important step forward in the loghandling art. The device of the patent utilizes pusher arms oftelescopic construction in conjunction with actuating links which serveto urge the lower sections of the pusher arms downwardly relative to theupper section as the pusher arms are swung away from the load supportingcarriage, whereby to enable the lower ends of the lower sections tofollow a path which is approximately parallel to the load supportingmeans, such as forks, during outward swinging actuation thereof byhydraulic motor means.

By use of such construction logs can be pushed from the ends of theforks while utilizing a pusher structure which is retractable, when notin use, to a non-interfering position relative to the carriage and forksso that the latter may be used for handling loads other than logswithout any loss in load-carrying capacity.

Despite the significance of the advance over the prior art of Brudisinvention, however, certain disadvantages have been encountered inpractice which it is the primary purpose of the present invention toovercome. A source of difficulty has developed in the use of theaforementioned telescopic pusher arms in that, under heavy loads, thearms tend to bend one relative to the other thereby causing a binding ofthe arms which either places undue strain on the mating parts asextension forces continue to be applied, or even causes the mechanism tofail to operate at certain times. In addition, the patented devicedepends upon hydraulic motor applied torque to effect operation of thearms. Utilization of a torque transmitted force within the spaceenvelope available requires, at times, the application of extremely highforces in order to operate the mechanism.

It is a primary object of the present invention to provide an improvedindustrial truck attachment of the type contemplated which eliminatesthe disadvantages of prior devices while retaining the advantagesthereof.

It is another object of the present invention to provide improved pushermeans wherein the lower end thereof atent is confined to a path oftravel which is approximately parallel to the load supporting meansduring outward swinging movement thereof so that certain kinds of loadsmay be discharged from the load supporting means.

It is a further object of the present invention to provide an improvedpusher attachment which is simple in construction, extremely efficientin operation, and economical to manufacture.

The structure, which enables the foregoing objects to be attainedcomprises generally a scissors-like linkage including a main pusher armand a link or radius rod which is connected to the arm intermediate itsends and to support means for the device, and a second link or radiusrod connected to the top portion of the arm and to said support means atlocations above the first link. Motor means is provided which directs apushing force on the scissors-like linkage such that the pusher armmoves outwardly of the load supporting means in a path of travel whichis approximately parallel thereto. The geometry of the interconnectedparts which comprise the attachment device is, of course, ofsignificance in enabling the pusher arm to follow the aforesaid path oftravel.

Now, in order to acquaint those skilled in the art with the manner ofconstructing and using pusher means in accordance with the principles ofour present invention, we shall describe in connection with theaccompanying drawings a preferred embodiment of our present invention.

In the drawings:

FIGURE 1 is a side elevational view of an industrial truck with theimproved pusher means of the present invention arranged at the forwardend thereof in extended position;

FIGURE 2 is a detailed side elevational view of the pusher attachmentwherein various attitudes of extension thereof are illustrated inphantom lines, the retracted position thereof being shown in full lines;

FIGURE 3 is a front elevational view of the attachmerit as shown inretracted position in FIG. 2, but with the fork tines removed; and

FIGURE 4 is a partial view of the machine as shown in FIG. 1, but withthe pusher attachment in retracted position.

Referring now to the drawings, there is indicated generally by thereference numeral 10 an industrial truck which has a main frame and bodyportion 12 supported on pairs of wheels 14 and 16 (one of each pairbeing shown). The main frame, at its forward end, supports a verticallydisposed mast structure 18. The mast in turn carries a load supportingcarriage defined by a pair of vertically spaced, transversely extendingbeam members 20 and 22 which are connected together by a pair oftransversely spaced, vertically extending channel members 32 and to themast structure by transversely spaced bracket means which is shownpartially at numeral 24 (FIGS. 2 and 3). Carriage member 22 carries apair of transversely spaced and forwardly extending fork tines 26 (onlyone of which is shown) which are pivotally connected at pivot means 28to a generally channel shaped transverse connecting beam 30 (FIG. 2)which is supported from the beam 22. The upstanding leg of each fork isformed to rest against the forward surface of beam 20 which reactsagainst the load supported by the fork (FIG. 2). It will be understoodthat the carriage and forks thereon are movable vertically up and downmast 18 in a conventional manner by hydraulic or other suitable means toraise and lower a load on the forks.

In the bottom portion of each channel beam 32 is secured a downwardlydepending member 34 having an opening therethrough in which is mounted apivot shaft 36. An upwardly and rearwardly extending bifurcated bracketmember 38 is secured to the upper end of each member 32 and supports atransverse pivot shaft 40 therein to which is pivotally connected anupstanding link member or radius rod 42 which is also pivotallyconnected at its opposite end to a transversely extending shaft member44. The shaft member 44 extends transversely outward of each link 42 andat each of its opposite ends supports for pivotal movement a mountingblock 46 from which depends an elongated downwardly extending mainpusher arm 48. A second main link member or radius rod 50 is pivotallysecured at its one end to each pusher arm 48 intermediate the endsthereof, and at its opposite end to pivot shaft 36. Link members 50 aremounted inwardly of pusher arms 48 and outwardly of link members 42, theupper ends thereof being pivotally mounted upon a connecting transverseshaft member 52 which extends through the pusher arms. Inwardly of eachlink member 42 is mounted a hydraulic cylinder and piston assembly 53,which is secured for pivotal movement upon a trunnion 54 located at theupper end of a bracket means 56 which is secured at its lower end tobeam 22. The piston rod of the hydraulic assembly is pivotally connectedto a bracket means 58 which is secured to transverse shaft 52.

When the hydraulic motors 53 are pressurized to cause extension thereofby remote control means, not shown, located in the drivers compartment,the various parts of the pusher device will be actuated from a positionof full retraction, as shown in FIGS. 3 and 4 and in the full lines ofFIG. 2, to an extended position as shown in FIG. 1 and in phantom viewin FIG. 2. When the pusher device is in a fully retracted position itwill be observed that the entire assemblage of parts lies rearwardly ofthe plane of the forward face of the forks 26 Where it will notinterfere with the engagement of loads other than logs, such asrectangular loads which may be stacked in abutment with the verticallegs of the forks rather than in a less stable position forwardlythereof. Thus, although the attachment is particularly adapted forhandling cylindrical objects such as logs, it neither limits the trucksolely to such use nor decreases its caapcity in handling other types ofloads.

It will be further observed that as the attachment is caused to extendfrom the retracted position thereof the paths followed by the lower endsof the pusher arms 48 are moved outwardly of the forks with the lowerends thereof maintained closely adjacent to the forks irrespective ofthe pivotal position of the pusher arms, as best seen in FIG. 2. Thepaths followed by the lower ends of the members 48 are actually slightlyserpentine; however, for all practical purposes these paths areapproximately parallel to the horizontal portions of the forks. Thisresult is eifected by the manner in which link members 42 and 50 areeach pivotally interconnected with the pusher arms and the carriageportion of the attachment. It will be observed that a scissorslikeaction is effected between links 50 and pusher arms 48 as the hydraulicmotors exert a direct pushing force upon the pivot shaft 52 whichinterconnects said links and arms. Shaft 52 moves in a circular areabout the axis of pivot shafts 36, the curvature being fixed by thelength of links 50 between the axes of shafts 36 and 52. At the sametime pusher arms 48 are caused to be pivoted in a counterclockwisedirection by link members 42 as the latter define circular arcs duringmovement thereof having radius equal to the distance between the axes ofpivot shafts 40 and 44. The relationship between the length of pairs oflink members 42 and 50, and the distances between the axes of pivotshafts 36 and 40 on the one hand and between pivot shafts 52 and 44 onthe other is such that a forwardly or rearwardly directed force appliedto shaft '52 effects movement of hte lower ends of the pusher arms inpaths which are approximately parallel to the horizontal portions of theforks. The geometry of the attachment 4 device is fully illustrated inFIG. 2. Thus, the pusher arms 48 are enabled to push off of the tips ofthe forks loads such as small diameter logs.

It will be observed that considerable advantage is to be derived in theutilization of a direct pushing force applied to shaft 52 by thehydraulic motors 53 rather than utilization of an arrangement whichnecessitates the application of torque forces as applied, for example,to the crank arms of the attachment device of the aforementioned patent.A substantially greater effective force is derived in the use of thepresent invention, given hydraulic motor means of certain capacity, thanin prior constructions. Also, the present structure tends to minimizethe stress to which certain of the various parts are subjected.

Now, while we have shown and described what we believe to be a preferredembodiment of our present invention, it will be understood that variousrearrange ments and modifications may be made therein without departingfrom the spirit and scope of our invention.

We claim:

1. For use with an industrial truck having a load supporting carriage,mechanism comprising first and second normally upright link meanspivotably supported by the carriage in vertically spaced relation toeach other, said second link means being longer than said first linkmeans, a pusher means pivotably supported from the upper ends of saidfirst and second link means, the pivotal connection of the first linkmeans to the pusher means being spaced longitudinally of and above theconnection of the second link means to be pusher means, the pivotalconnection of each link means to the pusher means being located aboveits respective connection to the carriage means, and motor meansoperatively connected to the pusher means for actuating same in swingingmovement outwardly of the carriage.

2. For use with an industrial truck having a load supporting carriage,mechanism comprising first link means, first pivot means connecting saidlink means to the carriage, second link means, second pivot meansconnecting the latter link means to the carriage at a location abovesaid first pivot means, pusher means, third pivot means connecting saidfirst link means to said pusher means intermediate the ends thereof,fourth pivot means conmeeting said second link means to said pushermeans above said third pivot means, said first link means being longerthan said second link means, and motor means operatively connected tothe pusher means for swinging same outwardly of the carriage withoutward swinging movement of the first and second link means in the samerotational direction.

3. A mechanism as claimed in claim 2 wherein the motor means isoperatively connected to the pusher means at a location which isadjacent the third pivot means, said motor means being adapted therebyto effect outward swinging movement of the pusher means by directapplication of a pushing force thereon.

4. For use with an industrial truck having a load supporting carriageand horizontal load supporting means extending forwardly therefrom,mechanism comprising pusher means operatively connected to the carriageand actuatable outwardly therefrom such that the lower end thereof canpush a load from the load supporting means, said operative connectionincluding first and second swingable link means pivotably connected invertically spaced relation to the carriage and to the pusher means, saidfirst link means comprising the lower link which is of greater lengththan the second upper link means, said first and second link means beingcooperable to swing dilferent portions of the pusher arm along arcs ofdiflferent radii during outward swinging movement thereof, and motormeans for actuating the pusher arm outwardly of the load supportingmeans, the lower end of the pusher arm being constrained by said firstand second link means to move in a path which is approximately parallelto the load supporting means.

5. For use with an industrial truck having a load supporting carriageand horizontal load supporting means extending forwardly therefrom,mechanism comprising a short link pivotally secured adjacent its one endto an upper portion of the carriage, a long link pivotally securedadjacent its one end to a lower portion of the carriage, pusher meanspivotally secured to the opposite ends of both said short and longlinks, said latter pivotal connections being displaced longitudinally ofeach other on said pusher means, and motor means connected to the pushermeans for actuating same outwardly of said carriage with said short andlong links, the lower end of said pusher means following a path which isapproximately parallel to the load supporting means.

6. A mechanism as claimed in claim 5 wherein said motor means comprisesa hydraulic cylinder and piston assembly supported by the carriage andconnected at its operating end adjacent said third pivot means forapplying a pushing force thereto which actuates the pusher arm outwardlyof the load supporting means.

7. For use with an industrial truck having a load supporting carriage,mechanism comprising first and second means pivotally connected to thecarriage in vertically displaced relation one to the other, pusher meanspivotally connected to both the first and second means at the endsthereof opposite the pivotal connections to the carriage, and actuatingmeans operatively connected to the pusher means for actuating same inswinging movement outwardly of the carriage, said first means tending toactuate the lower end of said pusher means downwardly during outwardswinging movement thereof, said second means tending to actuate thelower end of said pusher means upwardly during outward swinging movementthereof, and said first and second means being combined with the pushermeans in such a manner that said downward and upward movement tendenciesof the lower end of the pusher means is essentially neutralized so thatsaid pusher means moves in a path which is approximately parallel to theground during outward swinging movement thereof.

8. For use with an industrial truck having a load supporting carriageand horizontal load supporting means extending forwardly therefrom, loadpush-01f attachment means comprising a pair of normally upright upperand lower radius rods pivotally supported by the carriage in verticallyspaced relation, the upper radius rod being pivotally mounted adjacentits lower end to an upper portion of the carriage, the lower radius rodbeing pivotally mounted adjacent its lower end to a lower portion of thecarriage transversely outwardly of and in partial overlapping relationto the upper radius rod, pusher means depending downwardly from andpivotally mounted upon the upper ends of both the upper and lower radiusrods, and hydraulic motor means pivotably connected to the upper end ofthe lower radius rod, extension of said motor means effecting outwardswinging movement of the pusher means with radial movement of said upperand lower radius rods such that the lower end of the pusher means movesin a path which is approximately parallel to the load supporting means.

9. An attachment as claimed in claim 8 wherein the upper radius rodmeans is of shorter length than the lower radius rod means and thepivotal connection of the upper radius rod means with said pusher meansis displaced above the pivotal connection of the lower radius rod meanswith said pusher means.

'10. An attachment as claimed in claim 8 wherein said pusher means isdisplaced transversely outwardly of said lower radius rod means and inoverlapping relation thereto.

11. An attachment as claimed in claim 10 wherein said upper radius rodmeans comprises a pair of transversely spaced link members, said lowerradius rod means comprises a pair of transversely spaced link members,and said pusher means comprises a pair of transversely spaced barmembers.

References Cited in the file of this patent UNITED STATES PATENTS2,601,931 Dunham et al July 1, 1952 2,742,167 Brudi Apr. 17, 1956

